<div id="root">
  <div data-field=a>This is a</div>
  <div id=a>This is not a</div>
  <div class=a>This is not a</div>

  <div id=b>This is b</div>
  <div class=b>This is not b</div>

  <div class=c>This is c</div>
  
  <div class="a b">This is not a or b</div>
  <div class="d  e f">This is d, e, and f</div>
</div>